1. Field of the Invention
The present invention relates to a cooling device for an electric apparatus mounted on a vehicle, and particularly relates to a cooling device for a power storage mechanism (a battery, a capacitor, and others), a PCU (Power Control Unit), and others used for an electric vehicle (EV), a hybrid vehicle (HV), and others.
2. Description of the Background Art
Each of an electric vehicle, a hybrid vehicle, and a fuel cell vehicle, which obtains driving force for the vehicle from an electric motor, is mounted with a power storage mechanism (a secondary battery (also referred to as a battery), a capacitor, and others). As to the electric vehicle, electric power stored in the power storage mechanism is used to drive an electric motor to thereby drive the vehicle. As to the hybrid vehicle, electric power stored in the power storage mechanism is used to drive an electric motor to thereby drive the vehicle, and an engine is assisted by the electric motor to thereby drive the vehicle. As to the fuel cell vehicle, electric power from a fuel cell is used to drive an electric motor to thereby drive the vehicle, and in addition to the electric power from the fuel cell, electric power stored in the power storage mechanism is used to drive the electric motor to thereby drive the vehicle.
A secondary battery (battery), which is an example of these power storage mechanisms, is required to output high voltage and high power, and hence a battery pack is formed by connecting approximately six battery cells such as lithium-ion batteries or nickel-hydrogen batteries of approximately 1.2 V in series to form a battery module, and connecting approximately 30-40 battery modules in series. The electric vehicle, the hybrid vehicle, and others must be mounted with such a voluminous secondary battery, which has not been mounted on the conventional vehicle that relies solely on the internal combustion engine as its driving source. From a viewpoint of effectively using a vehicle interior space and a luggage compartment space, assuring safety in the case of collision, and others, it is necessary to consider the position in the vehicle for mounting the secondary battery, which has a relatively large volumetric capacity among the electric apparatuses to be mounted on the vehicle. Furthermore, it is necessary to consider the position for mounting an inverter and a DC/DC converter, which are referred to as a PCU.
In this consideration, it is necessary to deliberate on the size of the secondary battery (a height, a length in a width direction of the vehicle, a length in a longitudinal direction of the vehicle), deliberate on uniform cooling of the secondary batteries because of Joule heat or heat liberation caused by a chemical reaction inside the secondary batteries, or deliberate on cooling of a heating element referred to as a power semiconductor and included in the PCU.
Japanese Patent Laying-Open No. 2001-167806 (Patent Document 1) discloses a vehicle-mounted battery pack which has a compact configuration, can easily be disposed in a small space in the motor vehicle, and can reduce variations in temperature among battery modules.
The vehicle-mounted battery pack is the one in which an assembled battery, which has a plurality of battery modules integrated therein into a rectangular parallelepiped shape, is accommodated in a battery accommodation case and mounted on the motor vehicle, characterized in that the assembled battery is disposed in the battery accommodation case in a manner tilted with respect to a bottom surface and a top surface of the battery accommodation case, such that one side portion of the assembled battery is located adjacently to the bottom surface of the battery accommodation case and the other side portion of the assembled battery is located adjacently to the top surface of the battery accommodation case, and also characterized in that a cross flow-type impeller is rotatably disposed inside the battery accommodation case such that the impeller extends along the entire one side portion of the assembled battery located adjacently to the bottom surface of the battery accommodation case.
The vehicle-mounted battery pack is configured such that cooling airflow is supplied to the entire assembled battery disposed in the battery accommodation case in a tilted manner, by the impeller disposed in the battery accommodation case. Therefore, the vehicle-mounted battery pack has a compact configuration and can be mounted in a small space in the motor vehicle. Furthermore, the battery modules in the assembled battery can be cooled efficiently and uniformly, and variations in temperature among the battery modules can be reduced.
Generally, after the cooling airflow supplied to the assembled battery cools (exchanges heat with) the assembled battery, it is exhausted to the vehicle interior or the outside of the vehicle (it may temporarily be exhausted to the vehicle interior, even if it is eventually exhausted to the outside of the vehicle). If air is exhausted to the vehicle interior in the same direction, a temperature of air in the vehicle interior may locally rise owing to, for example, air exhausted from the assembled battery installed on a floor panel under a rear seat. Furthermore, if the local temperature rise occurs at the lower portion of the rear seat, the exhaust airflow impinges upon the feet of a passenger/passengers sitting on the rear seat (on the right side or the left side, or the both sides), or warms the feet (uncomfortable feeling occurs).
However, Patent Document 1 merely describes that the cooling airflow, which passes through spacing among battery modules in the assembled battery, flows into a space under the assembled battery in the battery accommodation case, and that a part of the cooling airflow is exhausted into the vehicle interior through an air vent provided at an air vent portion, and another part of the cooling airflow passes through an exhaust port, a battery-installed surface, and an exhaust guide provided at the bottom surface, and is exhausted into the exhaust duct, through which it is exhausted to the outside of the vehicle. In other words, a part of air that has cooled the assembled battery is exhausted into the vehicle interior, and another part thereof is exhausted to the outside of the vehicle. However, air is exhausted into the vehicle interior in a single direction. Therefore, as described above, the temperature of air in the vehicle interior may rise locally in the vehicle interior. On the other hand, it is difficult to freely provide an exhaust duct in the hybrid vehicle for mounting a voluminous assembled battery, which has not been mounted on the conventional vehicle that relies solely on the internal combustion engine as its driving source. Depending on the position where the assembled battery is mounted, for example, there is also a case where air that has cooled the assembled battery must exclusively be exhausted into the vehicle interior. In such a case, the possibility of the local temperature rise of air in the vehicle interior may arise more remarkably.